The temperature at which a black body of unit area loses its energy at the rate of $1 \text{ J/s}$ is:

The surface area of a person is $1.9 \, m^2$,their body temperature is $37 \, ^oC$,and the room temperature is $22 \, ^oC$. If the temperature of the skin is $28 \, ^oC$,find the rate of heat emission. The emissivity of the skin is $0.97$.

The power radiated by a black body is $P$ and it radiates maximum energy at wavelength $\lambda_0$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4}\lambda_0$,the power radiated by it becomes $nP$. The value of $n$ is

$A$ tungsten body of diameter $2.3 \ cm$ is at $2000 \ ^oC$. It radiates $30 \%$ of the energy radiated by a black body of the same radius and temperature. Find the radius of a black body which will radiate energy at the same rate at the same temperature (in $cm$).

$A$ black body of mass $34.38 \ g$ and surface area $19.2 \ cm^2$ is at an initial temperature of $400 \ K$. It is allowed to cool inside an evacuated enclosure kept at a constant temperature of $300 \ K$. The rate of cooling is $0.04 \ ^{\circ}C/s$. The specific heat of the body in $J \ kg^{-1} \ K^{-1}$ is (Stefan's constant $\sigma = 5.73 \times 10^{-8} \ W \ m^{-2} \ K^{-4}$)

If the temperature of the sun were to be increased from $T$ to $2T$ and its radius from $R$ to $2R$,then the ratio of the radiant energy received on the earth to what it was previously will be